Movement detection circuit for a PAL television signal

Abstract

Movement detection in a PAL television signal is effected on that portion of the television signal which is located within the chrominance signal band. This portion (obtained via 3) is demodulated into color difference signals (11, 13) which are added (29) and subtracted (27). The subtracted signal is delayed for one picture period and combined (39) with the added signal. Then the absolute value is produced (45), so that a signal is obtained which only reports movement and does not interpret crosstalk from the luminance signal of a still picture to the chrominance signal as movement.

What is claimed is: 
     
       1. A movement detection circuit for a PAL television signal containing a luminance signal and a chrominance signal having two quadrature components u(t) sin wt and ±v(t) cos wt, this movement detection circuit comprising a picture delay circuit, characterized in that the movement detection circuit further comprises demodulation circuit means for the chrominance signal, a combining circuit (3) and a filter circuit (3) to obtain a signal of the shape (u(t)-u'(t))±(v(t)-v'(t)), wherein u'(t) and v'(t) are demodulated chrominance signal components which are delayed relative to u(t) and v(t) by a time delay provided by the picture delay circuit, the demodulated single sideband components in this signal being suppressed and this signal being conveyed through an absolute value-producing circuit. 
     
     
       2. A movement detection circuit as claimed in claim 1, characterized in that the filter circuit comprises a band-pass filter, for suppressing that portion of the television signal which does not contain chrominance signal components, coupled to an input of the demodulation circuit means which demodulates the chrominance signal into two color difference signals one of which changes its sign from horizontal deflection period to horizontal deflection period, and the movement detection circuit further comprises an added circuit and a subtracting circuit for adding and subtracting, respectively, the demodulated color difference signals, the picture delay circuit and the combining circuit for combining the signal from the subtracting circuit delayed by the picture delay circuit and the undelayed signal from the adder circuit, being coupled to the substracting circuit, while the absolute-value producing circuit is coupled to an output of the combining circuit. 
     
     
       3. A movement detection circuit as claimed in claim 2, characterized in that the movement detection circuit further comprises an adder circuit having an input coupled to an output of the absolute-value-producing circuit and a further input coupled to the output of the absolute-value producing circuit via a delay circuit producing a delay of one horizontal deflection period. 
     
     
       4. A movement detection circuit as claimed in claim 1, characterized in that the movement detection circuit further comprises an adder circuit having an input coupled to an output of the absolute-value-producing circuit and a further input coupled to the output of the absolute-value producing circuit via a delay circuit producing a delay of one horizontal deflection period.